The ability to efficiently separate mixed materials, such as household recycling and construction waste, is of increasing importance and economical significance. For example, efficiently extracting and separating various types of recyclable materials from variable mixed waste streams is a critical factor when considering the economic viability of a recycling program. Material Recovery Facilities (MRFs) must be able to separate or sort mixed recyclable materials to a significantly high purity, for example 10 percent. If the final sorted and bailed product, for example similar plastic materials, does not achieve the purity required for purchase on the commodity market at a desired price, the product represents wasted resources and a financial loss for the MFR.
A critical step in the sorting or separation process is the dimensional sorting of materials. Several types of dimensional sorting equipment or separators have been developed, however each of these known types of separators continues to suffer from significant shortcomings. Ballistic-type separators function by rotating an angled surface in a relatively small vertical circle, thereby projecting the mixed materials deposited upon the surface into the air. The materials are separated according to each materials ballistic properties and trajectory created by the movement of the surface.
These types of separators may employ a surface that is unitary or one that is divided into various portions or sections that may move in unison or separately relative to one another. However, in order to achieve the desired motion of the surface, known separators employs a plurality of different motors. For example, different motors may be associated with each of the sides or corners of the unitary surface or with each of the various portions or sections of the surface. An obvious shortcoming of these separators is the increased maintenance associated with the calibration of the multiple motors to achieve the desired movement of the surface.
Another type of dimensional separator employs an angled surface formed of a bank of vertically rotating discs. The discs may have a roughly triangular or irregular shape and may be oriented non-symmetrically along axles or shafts. The axles rotate the discs towards an elevated side of the surface, thereby carrying certain materials up the surface while other materials fall towards the lower side of the surface. One obvious shortcoming of disc-type separators is the increased maintenance resulting from the wear associated with a surface formed of entirely moving parts, e.g. discs, axles, bearing.
Another disadvantage with disc-type separators is a propensity for materials to wrap themselves around and attach themselves to the discs and rotating spaces between the discs. These wrapped materials can lead to decreased throughput and efficiency due to the equipment's down-time required to remove the materials and increased impurities due to the effect of the wrapped materials on the migration of other materials. On disc-type systems employing multiple drive motors, required maintenance may also be undesirably high due to the need to calibrate the efforts of the different motors.
Finally, both of the above types of separator sort small materials or fines by providing voids or holes in the surface through which the fines can pass. The fines pass through the surface and ultimately into a vessel or onto a conveyor belt for transfer. However, known separators suffer from the fact that the fines must fall over equipment structure residing under the surface and above the output vessel or conveyor belt. These structures include drive motors and other moving and often sensitive attachments points of the equipment. This separation technique has the shortcoming of resulting in increased maintenance and repair due to the falling fines contaminating or damaging the components of the separator residing under the surface and above the output.
In view of the above described failures of the known dimensional separators, there exists a significant need in the art for more robust separators having increased efficiency and decreased maintenance and repair costs.